tempco resistors

[Don Tillman]

   Date: Wed, 01 May 96 09:39:02 PDT
   From: gstopp at fibermux.com

   It's not a stupid question - it took me years to understand this and 
   I'm still not sure I got it right. But I'll try...

That explanation seems a little confusing, Gene.  I'd say that the
crux of the biscuit is that the transistor junctions responsible for
exponential control are completely temperature sensitive, and, while a
second matched transistor junction at the same temperature can be
employed to compensate for the temperature sensitivity, there's a more
subtle effect (it shows up in scaling accuracy) that the tempco
resistor takes care of.

Thus, exponential converters that employ thermostatically-controlled
heaters don't need tempco resistors.

  -- Don